Diamond is an allotrope of carbon exhibiting a crystallographic network comprising exclusively of covalently bonded, aliphatic sp.sup.3 hybridized carbon atoms arranged tetrahedrally with a uniform distance of 1.545 .ANG. between atoms. Diamond is extremely hard having a Mohs hardness of 10. It exhibits four times the thermal conductivity of copper and it is electrically insulating. Its hardness and thermal properties are but two of the characteristics that make diamond useful in a variety of industrial components. Initially non-gem quality natural diamonds were used in a variety of abrasive applications but with the invention of synthetic diamonds by high pressure/high temperature techniques, a spectrum of additional products have found favor in the marketplace. However, the requirement of high pressure and high temperature has been a limitation in preventing extensive usage of synthetic diamonds.
Recent industrial efforts directed toward the growth of diamonds at low pressures has dramatically increased the feasibility of using diamonds in various industrial applications. Low pressure growth of diamond has been dubbed "chemical vapor deposition" or "CVD" in the field. In the CVD process diamonds are grown at low pressures from hydrocarbon gases in the presence of atomic hydrogen. Many methods have been disclosed for growing diamonds metastably and generally these methods differ from each other by the way in which atomic hydrogen, a key reactant, is generated and transported within the system. For a general summary of various diamond deposition methods including CVD methods, reference is made to Bachmann, et al., Diamond Thin Films, Chemical & Engineering News, 67(20), 24-39 (May 15, 1989), to Bhat, D., Chemical Vapor Deposition, Surface Modification Technologies, An Engineer's Guide, edited by Sudarshan, T., 1989 Edition, Marcel Dekker, Inc., New York, N.Y., pages 141-218, and to Hocking, M., Vasantasree, V., and Sidky, P., Chemical Vapour Deposition, Metallic & Ceramic Coatings: Production, High Temperature Properties & Application, Longman Scientific & Technical Group, England (U.K.) copublished with John Wiley & Sons, New York, N.Y., pages 103-172, all incorporated herein by reference.
When a free standing diamond film for example having a funnel shape is desired, it is very cumbersome and invariably impractical to prepare a substrate on which such a film could be deposited. In one of the prior art methods a funnel shape is machined from a tubular shape. However it is very difficult and expensive to machine material such as diamond to the degree of precision required in high pressure water jet cutting systems. For a general summary of various hydro-machining methods including water jet cutting methods, reference is made to a special report on Wet Grit, Abrasive Waterjets, American Machinist, October 1989, Penton Publishing, Inc., Cleveland, Ohio, pages 84-97 and to Guha, J., High-Pressure waterjet Cutting: An Introduction, Ceramic Bulletin, Vol. 69, No. 6, 1990, pages 1027-1029, both incorporated herein by reference.
A method directed to machining a funnel shape on a substrate, depositing a funnel material on the funnel shape, separating the funnel from the substrate, depositing diamond on the funnel and then separating the funnel shaped diamond article from the funnel has been disclosed. However, by way of example, it is difficult to deposit the funnel material on a funnel shape having a small diameter stem of about 0.500 millimeter outer diameter and having a long funnel length of about 75 millimeters. The present invention is directed to addressing the problem of making such funnel shaped articles.